Rachael, 32, suffers from bad PMS, but she has a trick to bring that phase to an end: After she has sex or masturbates, she gets her period by the next morning, if not right after. Cortne, 26, sometimes finds that her period is late — but she’s figured out a similar solution: She invites a partner over to have sex, and boom, it’s there the moment he pulls out.
When Miranda, 27, has sex while her period is late, it always arrives the moment she orgasms. The situation for Sarah, 29, is more unusual: She’ll go months without getting her period, then when she starts dating someone or becomes sexually active, she’ll start getting it again.
Many women report this phenomenon of sex bringing on their periods, but to doctors, it’s something of a mystery. In fact, despite how uncanny the timing appears, some say it’s merely coincidence.
“Sexual intercourse does not cause changes in the menstrual cycle of women,” says Amanda Shea, PhD, head of science at Clue. “Once you are in the luteal phase, after ovulation at day 14, you will get your period in 14 days. This happens regardless of sexual activity in a natural, typical 28-day cycle.”
“There is no data on such things, so any time unexpected bleeding occurs, it should never be assumed to be due to sexual intercourse,” agrees Felice Gersh, M.D., OB/GYN and founder/director of the Integrative Medical Group of Irvine. If the bleeding after sex happens when your period is not already on its way, it’s especially unlikely to be due to your period.
While some women report getting their periods right after sex, and there are a few possible ways that it might conceivably occur, there’s no solid evidence for it.
But if we want to speculate, there are a few potential ways sex might bring on someone’s period if it’s already on its way. It’s possible, for example, that very vigorous thrusting against the cervix could move the uterus in a way that releases the uterine lining shed during your period, says Gersh.
As Miranda experienced, the trigger could also be orgasm. Since orgasms involve uterine contractions, they can cause your body to push the blood out, Gersh explains. However, she says, “having an orgasm should not cause bleeding unless the period is right about to begin.” If sex commonly brought on your period when it wasn’t already starting, it would be very difficult to get pregnant because the embryo would have no place to implant, Shea points out.
Sarah’s pattern is more perplexing. The only possible explanation could be that her period is stopping due to stress, and her relationships are providing stress relief, says Deborah Lee, a sexual and reproductive healthcare specialist doctor for Dr. Fox Online Pharmacy. “Emotions are a key player in female health and function, so although unlikely, it could [be possible] that a new romantic relationship could not affect one’s hormonal cycles,” says Gersh.
However, if you find yourself bleeding after sex, it’s a good idea to see a doctor, because it could be something other than your period, says Lee. Post-coital bleeding affects up to six percent of women within a year and can be caused by chlamydia (which sometimes won’t involve other symptoms), cervical ectropion, cervical infections, cervical polyps, or (less commonly) cervical cancer.
“The vagina can also get lacerated during sex if there is not sufficient lubrication,” says Shea. “Anyone who is having postcoital bleeding should be seen by their gynecologist.”
Getting your period after sex could also be a product of your birth control. If it happens when your period isn’t due, this could mean you’re not using your birth control correctly, says Lee. “If you miss pills or don’t follow the instructions correctly, this can result in unscheduled bleeds,” she explains.
“Sometimes a bleed — triggered by the hormones in the birth control — can result in blood building up inside the womb, and the physical jostling around that happens when you have sexual intercourse can cause it to be released at or after the event,” says Lee. Other times, it’s just coincidence when birth-control-triggered bleeding happens during sex.
In short, while some women report getting their periods right after sex, and there are a few possible ways that it might conceivably occur, there’s no solid evidence for it. So, if this happens to you, see an OB/GYN to make sure there isn’t anything else going on.
That said, sex and orgasms are stress- and pain-relieving, so you can continue to enjoy them before, during, and after your period, whether they affect your cycle or not. As Rachael puts it, “Best-case scenario, I get my period sooner, meaning I get to be done with it sooner, too. And worst-case scenario, I get orgasms. It’s a pretty win-win situation.”